This invention relates to servo systems and more particularly to a system for correcting lateral deviations of a transducer from a desired path with respect to a recording medium.
The track to track spacing of disk files has been continually reduced as a function of track following technology improvements. The physical width of the capture area, or region where the position error signal is a linear function of head displacement from track center, has been shrinking as the number of tracks per inch has been increasing. Hard file memories are being required to possess faster and faster track accessing. Furthermore, less servo information is being made available to the track access hardware, particularly when sector servo schemes are employed which only yield servo information for a small portion of time per sector and once each sector.
Sector servo relates to the fact that the disk may be informationally divided up into sectors (much as one would cut a pie). Each sector is further divided into a servo information subsector and a data information subsector. Positional information is only available while the magnetic transducers are over a servo information subsector. Super synchronous access refers to an access where tracks are crossed at a rate greater than the rate of servo position information occurrence. The implication of this is that position information may not be available at the time each track is crossed. Therefore, the access mechanism must assume track crossings based on ballistics and Newton's laws where there is not real time verification of track crossings.
Two facts, first, that files are trying to move faster during access than they have heretofore and second, that there is less space alloted on the disk for the track follow and access hardware to receive current, accurate information, would mandate larger track capture areas where the position error signal is a linear function of the head's displacement from the track centerline.